| 摘要 |
The present invention relates to a measurement instrument of the folding rule type with four rigid and jointed branches 1-4 of equal length, which can be used for measuring lengths and as a bevel square with direct angle reading from 0 to 180 DEG or of percentage incline. This instrument is characterised in that when the four branches 1-4 are spread out, one of the faces of the rule thus constituted is graduated in units of length, two consecutive branches 1, 2; 2, 3, are used as a bevel square and the other two branches 3, 4; 1, 4, longitudinally unfolded and extending along the base of the isosceles triangle formed by the bevel square 1, 2; 1, 3, have a graduation, over their free face, proportional to the sine of half the angle a formed by the two branches 1, 2; 1, 3 constituting the bevel square according to the known relationship linking the angle at the vertex a of the isosceles triangle to the length of its base. <IMAGE>
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